CRITICAL APPRAISAL OF A TRIAL
RCT WORKSHEET
Citation:
Are the results valid?
1. Was there a clearly defined, focused
research question? What was the study
question?
2. Was the assignment of patients to
treatments randomised?
-Was randomisation (allocation) concealed?
3. Were all patients who entered the trial
accounted for at its conclusion? -and were
they analysed in the groups to which they
were randomised (intention-to-treat
analysis)?
4. Were subjects in the treatment and
control groups similar with respect to known
prognostic variables?
5. Were patients aware of group allocation?
6. Were clinicians aware of group
allocation?
7. Were outcome assessors aware of group
allocation?
Source: Adapted from 1) Centre for Evidence Based Medicine (http://www.cebm.net/); 2) Badenoch & Heneghan,
Evidence-based Medicine Toolkit, BMJ Books, 2002; and 3) Guyatt & Rennie. Users’ Guides to the Medical
Literature, AMA Press, 2002.
Compiled by Madhu Pai [madhukar.pai@mcgill.ca]
1
CRITICAL APPRAISAL OF A TRIAL
RCT WORKSHEET
8. Was duration of follow-up adequate? Was
follow-up complete?
Any other potential biases in this study?
Potential for selection bias?
Potential for information bias?
Potential for confounding?
Was there a clear rationale for the sample
size/power estimation?
What were the primary and secondary
endpoints of the study? How well were the
endpoints measured?
Were surrogate endpoints used?
Were the data analytic methods appropriate
for the research question and study design?
Source: Adapted from 1) Centre for Evidence Based Medicine (http://www.cebm.net/); 2) Badenoch & Heneghan,
Evidence-based Medicine Toolkit, BMJ Books, 2002; and 3) Guyatt & Rennie. Users’ Guides to the Medical
Literature, AMA Press, 2002.
Compiled by Madhu Pai [madhukar.pai@mcgill.ca]
2
CRITICAL APPRAISAL OF A TRIAL
RCT WORKSHEET
What are the results?
SAMPLE CALCULATIONS:
Occurrence of endpoint
(outcome)
Control Event
Rate
[CER]
Experimental
Event Rate
[EER]
9.6%
2.8%
Relative Risk
Reduction
RRR
CER - EER
CER
9.6% - 2.8%
9.6%
= 71%
Absolute Risk
Reduction
ARR
CER - EER
Number Needed
to Treat
NNT
1/ARR
9.6% - 2.8% = 6.8%
(4.3% to 9.3%)
1/6.8% = 15 pts,
(11 to 23)
95% Confidence Interval (CI) on an NNT = 1 / (limits on the CI of its ARR) =
YOUR CALCULATIONS:
CER
EER
Relative Risk
Reduction
RRR
CER - EER
CER
Absolute Risk
Reduction
ARR
CER - EER
Number Needed
to Treat
NNT
1/ARR
What are the trial results?
1. How large was the treatment effect
(e.g. relative risk reduction and absolute
risk reduction)?
2. How precise was the estimate of the
treatment effect (i.e. confidence intervals
around the point estimates or p-values)?
Source: Adapted from 1) Centre for Evidence Based Medicine (http://www.cebm.net/); 2) Badenoch & Heneghan,
Evidence-based Medicine Toolkit, BMJ Books, 2002; and 3) Guyatt & Rennie. Users’ Guides to the Medical
Literature, AMA Press, 2002.
Compiled by Madhu Pai [madhukar.pai@mcgill.ca]
3
CRITICAL APPRAISAL OF A TRIAL
RCT WORKSHEET
Can you apply the results to patient care?
1.Were the study patients similar to the
patient in your practice?
-Does your patient match the study
inclusion criteria?
-If not, are there compelling reasons why
the results should not apply to your patient?
2. Were all clinically important outcomes
considered?
3. Are the benefits worth the costs and
potential risks?
-What is the number needed to treat (NNT)
to prevent one adverse outcome or produce
one positive outcome?
-Is the reduction of clinical endpoint worth
the increase of cost and/or risk of harm?
In summary:
What are the major strengths of this study?
What are the major limitations of this study?
Are there any major ethical concerns with this study?
Source: Adapted from 1) Centre for Evidence Based Medicine (http://www.cebm.net/); 2) Badenoch & Heneghan,
Evidence-based Medicine Toolkit, BMJ Books, 2002; and 3) Guyatt & Rennie. Users’ Guides to the Medical
Literature, AMA Press, 2002.
Compiled by Madhu Pai [madhukar.pai@mcgill.ca]
4